Ontogenetic asynchrony in fish migrations may lead to disparate parasite assemblages: Implications for its use as biological tags

•Fish age and size have a strong influence on the structure of parasite assemblages.•Similarity in parasite assemblages decreases as differences in host size increase.•Parasite communities in younger specimens are more heterogeneous and stochastic.•Ontogenetic change in parasite loads is enhanced by age-related asynchronic migrations.•Parasite tags must be used cautiously if asynchronous and divergent migrations occur.